ERSE high quality copper foil coils are made from high purity 99.99%
copper foil and a thin high purity BOPP polypropylene film. The
surface area of copper foil eliminates skin effect seen in some air
core inductors and improves mechanical stability thereby
eliminating microphonic distortion. The reduced skin effect allows
the DC resistance to track the A.C. resistance making for an ideal
inductor.